A prism ABC (with BC as base) is placed in different orientations. A narrow beam of white light is incident on the prism as shown in Figure 11.1. In which of the following cases, after dispersion, the third colour from the top corresponds to the colour of the sky?

fig 11.1.jpg

(a) (i)

(b) (ii)

(c) (iii)

(d) (iv)



A prism splits white light into 7 colours with red at the top . The sequence of colours is ROYGBIV wrt to the base of the prism

When we invert the prism withe light at the same angle as before, the sequence gets inverted to VIBGYOR , with blue as the third colour from the top. 

Splitting of light in prism is kept in different orientation-01.jpg

So, the correct answer is (b)

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CA Maninder Singh is a Chartered Accountant for the past 14 years and a teacher from the past 18 years. He teaches Science, Economics, Accounting and English at Teachoo